Is the balance "adjustible"... or does it have to be reground or something?

Ray;

This is done in much the same fashion as with other similar rotating machinery such as fans and tires, but unlike tires there is no wear on these which would change balance. They are more like fan blades.

Stay tuned. It will become clear with time. I am not at that point yet by any means. I am just at the point of testing and proving the adjustment is needed, I am not at the stage of even determining if it is harmful or what the speed limitation is (if any) let alone doing it, let alone having the designer do the adjustment.